The present invention relates to a positive photoresist composition for use in the production of semiconductor integrated circuit device, mask for production of integrated circuit, printed wiring board, liquid crystal panel and the like.
As the positive photoresist composition, chemical amplification system resist compositions described in U.S. Pat. No. 4,491,628 and European Patent No. 29,139 are known. The chemical amplification-type positive resist composition is a pattern-forming material in which a reaction takes place utilizing an acid generated on an exposed area with irradiation of actinic ray or a radiation such as far ultraviolet ray as a catalyst to thereby differentiate the solubility in a developer between the area exposed and the area not exposed, thereby providing a pattern on a substrate.
The chemical amplification-type positive resist composition can be roughly classified into a three-component system comprising an alkali-soluble resin, a compound capable of generating an acid by the exposure to a radiation (photo-acid generator) and a dissolution-inhibiting compound for the alkali-soluble resin, a two-component system comprising a resin having a group capable of decomposing by the reaction with an acid to thereby become alkali-soluble and a photo-acid generator, and a hybrid system comprising a resin having a group capable of decomposing by the reaction with an acid to thereby become alkali-soluble, a low molecular weight dissolution-inhibiting compound having an acid-decomposable group and a photo-acid generator.
JP-A-9-319092 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses that a resin in which an acetal group having introduced thereinto an oxy linkage is introduced is effective in reducing the standing wave.
Also, JP-A-10-221854 discloses a resin having a substituted acetal group unit.
However, these resins having an acetal group form a round top shape and the rectangular property of profile is deficient, and in particular, development defect is in need of improvement.
The object of the present invention is to provide a chemical amplification-type positive photoresist composition having high sensitivity and high resolution, being improved in the development defect and rectangular property, and causing substantially no surface roughness.
Under these circumstances, the present inventors have made extensive investigations and found that the above-described object can be attained by using a positive photoresist composition comprising a compound containing an acid-decomposable group having a specific structure. The present invention has been accomplished based on this finding.
More specifically, the object of the present invention can be attained mainly by the following positive photoresist compositions.
(1) A positive photoresist composition comprising:
(a) a resin which has a structural unit having a group represented by the following formula (X) and is capable of decomposing by the action of an acid to increase the solubility in an alkali developer, and
(b) a compound capable of generating an acid with irradiation of actinic ray or radiation: 
wherein R1 and R2, which may be the same or different, each represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, R3 and R4, which may be the same or different, each represents a hydrogen atom or a linear, branched or cyclic alkyl group which may have a substituent, R5 represents a linear, branched or cyclic alkyl group which may have a substituent, an aryl group which may have a substituent or an aralkyl group which may have a substituent, m represents an integer of from 1 to 20, and n represents an integer of from 0 to 5.
(2) A positive photoresist composition comprising:
(a) a resin having structural units represented by the following formulae (I), (II) and (III) and being capable of decomposing by the action of an acid to increase the solubility in an alkali developer, and
(b) a compound capable of generating an acid with irradiation of actinic ray or radiation: 
wherein R21 represents a hydrogen atom or a methyl group, R22 represents a group incapable of decomposing by the action of an acid, R23 represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, an acyl group or an acyloxy group, n represents an integer of from 1 to 3 and W represents a group represented by the above formula (X).
(3) The positive photoresist composition as described in the above item (2), wherein the ratio of structural formulae (I), (II) and (III) satisfies the following conditions (i) to (iv):
0.1 less than (I)/[(I)+(II)+(III)] less than 0.25, xe2x80x83xe2x80x83(i)
1 less than (II)/[(I)+(II)+(III)] less than 0.15, xe2x80x83xe2x80x83(ii)
(I) greater than (II), and xe2x80x83xe2x80x83(iii)
0.5 less than (I)/[(I)+(II)] less than 0.85 xe2x80x83xe2x80x83(iv)
(wherein (I), (II) and (III) each represents a molar fraction of a structural unit having a group represented by formula (I), (II) or (III), respectively).
(4) The positive photoresist composition as described in any one of the above items (1) to (3), wherein the compound (b) capable of generating an acid with irradiation of actinic ray or radiation is at least one of the compounds capable of generating a sulfonic acid with irradiation of actinic ray or radiation, represented by the following formulae (A-1), (A-2), (A-3), (A-4), (A-5), (A-6) and (A-7); 
wherein R1 to R5, which may be the same or different, each represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, a hydroxy group, a halogen atom, or xe2x80x94Sxe2x80x94R6 (wherein R6 represents an alkyl group or an aryl group), and Xxe2x88x92 represents an anion of benzenesulfonic acid, naphthalenesulfonic acid or anthracenesulfonic acid having 1) at least one group selected from the group consisting of a branched or cyclic alkyl or alkoxy group having 8 or more carbon atoms, 2) at least two groups selected from the group consisting of a linear, branched or cyclic alkyl or alkoxy group having from 4 to 7 carbon atoms, 3) at least three groups selected from the group consisting of a linear or branched alkyl or alkoxy group having from 1 to 3 carbon atoms, 4) from 1 to 5 halogen atoms, or 5) a linear or branched ester group having from 1 to 10 carbon atoms; 
wherein R7 to R10, which may be the same or different, each represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, a hydroxy group or a halogen atom, Xxe2x88x92 has the same meaning as defined above, and m, n, p and q represents an integer of from 1 to 3; 
wherein R11 to R13, which may be the same or different, each represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, a hydroxy group, a halogen atom or xe2x80x94Sxe2x80x94R6, Xxe2x88x92 has the same meaning as defined above, l, m and n, which may be the same or different, each represents an integer of from 1 to 3, and when l, m and n each is 2 or 3, two groups out of two or three R11, R12 or R13 groups may be combined with each other to form a ring consisting of from 5 to 8 elements, including a carbocyclic, heterocyclic or aromatic ring; 
R14 to R16, which may be the same or different, each represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, a hydroxy group, a halogen atom or xe2x80x94Sxe2x80x94R6, R6 and Xxe2x88x92 have the same meanings as defined above, l, m and n, which may be the same or different, each represents an integer of from 1 to 3, and when l, m and n each is 2 or 3, two groups out of two or three of each of R14, R15 and R16 groups may be combined with each other to form a ring consisting of from 5 to 8 elements, including a carbocyclic, heterocyclic or aromatic ring; 
wherein Y represents a linear, branched or cyclic alkyl group which may be substituted, an aralkyl group which may be substituted, or 
wherein R31 to R51, which may be the same, each represents a hydrogen atom, a linear, branched or cyclic alkyl, alkoxy, acyl, acylamino, sulfonylamino, aryl, acyloxy, aralkyl or alkoxycarbonyl group which may have a substituent, a formyl group, a nitro group, chlorine atom, bromine atom, iodine atom, a hydroxyl group or a cyano group, and two of R31 to R35, two of R36 to R42, or two of R43 to R51 may be combined to form a 5-, 6-, 7- or 8-membered ring consisting of a carbon and/or hetero atom, provided that Y may be combined with a residue of another imido sulfonate compound, and X represents a linear or branched alkylene group which may have a substituent, a monocyclic or polycyclic alkylene group which may have a substituent or may contain a hetero atom, a linear or branched alkylene group which may be substituent, a monocyclic or polycyclic alkenylene group which may be substituted or may contain a hetero atom, an arylene group which may be substituted, or an aralkylene group which may be substituted, provided that X may be combined with another imido sulfonate residue; and
Ar1xe2x80x94SO2xe2x80x94SO2xe2x80x94Ar2 xe2x80x83xe2x80x83(A-7)
wherein Ar1 and Ar2, which may be the same or different, each represents a substituted or unsubstituted aryl group.
(5). The positive photoresist composition as described in any one of the above items (1) to (4), which further contains a cyclic amine compound.
(6) The positive photoresist composition as described in any one of the above items (1) to (5), which further contains at least one of a fluorine surfactant and a silicon surfactant.
(7). The positive photoresist composition as described in any one of the above items (1) to (6), which further contains a compound capable of decomposing by the action of an acid to increase the solubility in an alkali developer.